BodyTom移动CT的辐射剂量和图像质量评估

Radiation dose and image quality assessment on BodyTom CT

目的 通过对新一代全身移动CT（BodyTom CT）与常用固定CT机的比较，对其辐射剂量和图像质量评估。方法 用CATPHAN 500性能测试体模评价图像质量，用常规的100 mm笔形电离室、CT聚甲基丙烯酸甲酯（PMMA）体部体模及头部体模测量辐射剂量（头模直径为160 mm，体部体模直径为320 mm，它们宽度均为140 mm）。结果 BodyTom CT的空间分辨率、密度分辨率与两类固定CT接近，差异无统计学意义（P〉0.05）。对比度噪声比（CNR）降低20%左右：头部扫描模式下，明显低于飞利浦64排CT和东芝320排CT（重建函数soft时，t=-4.82、-6.98，P〈0.05；重建函数standard时t=-20.60、-20.09，P〈0.05）；体部扫描模式下，也明显低于飞利浦64排CT和东芝320排CT（重建函数soft时，t=-5.67、-12.82，P〈0.05；重建函数standard时，t=-3.39、-9.18，P〈0.05；重建函数sharp时，t=-3.88、-3.21，P〈0.05）。BodyTom CT的辐射剂量高于固定CT，相同参数下体部体模比飞利浦64排CT机剂量高22.97%（t=9.48，P〈0.05），比东芝320排CT机高29.60%（t=11.66，P〈0.05）；头模比飞利浦64排CT机高29.76%（t=23.44，P〈0.05），比东芝320排CT机高33.22%（t=23.11，P〈0.05）。结论 移动CT的图像与常规CT图像质量相当时，辐射剂量增高20%以上。

Objective To evaluate and compare the radiation dose and image quality of the new generation of whole body mobile CT （BodyTom CT） with commonly used fixed CT. Methods The image quality was evaluated with CATPHAN 500 performance test body model. The radiation dose was measured by conventional 100 mm pen ionization chamber and PMMA body phantom and head phantom （head diameter 160 mm,phantom diameter 320 mm and width 140 mm）. Results The spatial and contrast resolution of BodyTom CT images were similar to two kinds of fixed CT（P〉0.05）. The CNR of image with BodyTom CT decreased by about 20%：In head scan mode, significantly lower than that with Philps 64 slice CT and Toshiba 320 slice CT （with soft, t=-4.82,-6.98,P〈0.05; with standard, t=-20.60,-20.09,P〈0.05）; in body scan mode, significantly lower than that with Philps 64 slice CT and Toshiba 320 slice CT （with soft, t=-5.67,-12.82,P〈0.05;with standard, t=-3.39,-9.18,P〈0.05; with sharp, t=-3.88,-3.21,P〈0.05）.The radiation dose with BodyTom CT was significantly higher than that with fixed CT：in body model, 22.97% than that with Philps 64（t=9.48,P〈0.05）, 29.6% than that with Toshiba 320 slice CT（t=11.66,P〈0.05）; in head model, 29.76% than that with Philps 64 slice CT（t=23.44,P〈0.05）, 33.22% than that with Toshiba 320 slice CT（t=23.11,P〈0.05）. Conclusions The radiation dose with mobile CT was over 20%higher than that with routine multi-row CT while with the similar image quality.